NA became NL
 

HI
My historical league began in 1871 with two leagues National Association and American Association when in 1876 the National Association became National league the history of N.A. became N.L. How to prevent it.

Michel

Unfortunately you need to self edit and be vigilant.

Get rid of AA in 1871 and only have NA as one league at start up. Then when 1876 rolls around, change the name of NA to NL in the MLB Settings and keep going until 1901 when the AL enters the fray which you can accomplish via Expansion if you want to be pure.

If you just want to change NA to NL, you can change it under MLB League Settings and League & Teams tab.

How to make National Association (1871-1875) remains and that the National League appears in 1876 while retaining the American Association until 1901

Michel

Not sure what your asking but it sounds like you want to follow the real expansion. Though the game uses the real players from 1871-1900, the team names are not the same as real life.
You will have to create the National Association manually by moving and importing or creating the teams. If you import i would suggest deleting players before doing so to avoid duplicate players.
You will need to either disable playoffs or use custom playoffs for a single league like the NA and NL at times. You will need to turn off expansion and add the AA manually. Then you will need to move and delete the teams when the AA folds. You will also need to import or create schedules, choose roster sizes and pitching rotations that will fit the league. There is quite a bit more running a 19th century league using real expansion and the real teams than the modern era.

I wanted to do something similar to this, however I wanted to start in 1876. I know how to edit the teams (logos, uniforms etc.), but the leagues are rather difficult. As you guys know, 1876 marked the inception of the National League. I wanted only one league in order to re-create the history. I had no idea how to do it. I went into League Settings but couldn't delete the AL and move those four teams to the NL.

You don't need to delete the AL just move the teams to the NL and import or create a schedule. Now this isnt as much a problem if you just want real teams and don't care about the teams having the correct players. though ou would need to turn off automatic expansion as the game would change the teams. Also turn off all star game as you have only 1 league and either disable or use custom playoffs.
If you want correct teams i think its a little more difficult. Where in the past you could modify the csv files in the database to get players to go to their actual real teams instead of having to use these fictional teams, ootp has dropped the ball on this and force us to use their 19th century expansion. Only way around it is to draft every player or use ootp17 till 1900.

Yes, you can. You just have to wait until after the game is created.

You must do it manually... Personally I keep the structure, empty AA untill it started (I use it too to send the Chicago team in 72 and 73 when the franchise is sleeping).

I know it isn't 100% real to have a two league ML from 1871, but keeping one empty is a way to keep all the stats of the NA and AA in the record book for the ML.

Never keep two teams in an empty league, your game will be stuck since it will want to make them play together (even if you have no schedule).